Inductance device



Patented 0.1.10, 1933 l v iffrcsoasai" H h a A mnUo'rAnoEpEvmE j RalpliM. CQGi-eenidge,Chatham, ma as signor to Bell Telephone Laboratories,Incorporated, vNew New york Y orlJr, N. Y., a corporation of ApplicationJanuary 30, 1931.. Serial Nb. 512397 f [11 p 8 Claim's.'.(Cl.1'l 1- 242) i invention relates to inductance devices and more especially to suchdevices in which'the inductance" may be adjusted lor varied;

" The addition of loading inductances a t'ele-- phone lines to improvetransmission has been carriedon'for a number of years in a manner whichis well known in the art, both in the case of simple telephone linesandin the case of phantorn telephone systems; To provideagobd trarise '10mission characteristics in a phantomed' system,

the two side circuits must be accuratelybalanced andconsiderabledifficulty has been experiencedin properly balancingthe sideand phantomcir-" a cuitsespeciallywhere very exacting requirements '15 are placedupon the circuitsas'to transmission characteristics. Cross-talk betweenthe phantom and side circuits is one ofv the "results of fanimperfect-balance or inductance, capacitance or re-;

7 s'istance. h This invention has as an object the improvementof thetransmissioncharacteristics of tele- Phbn ir stion of cross-talk betweenside and phantom cirmm; g 4 A further object is the accurate loading oftelephone lines." ,5

"3 0 phantom circuits cf'a telephone line."

.o f theelectrical"characteristics, namely,

capacitanceandinductance being byjtheir nature complementary; can beadjusted for bythe inclu-J I sion in the circuit of the correct value ofeither. "85; Generally, however,an inductance deviceis used.

.ffIh'e objects of thisjinveritionfare attained by, inserting auxiliaryadjustable inductances in the circuits/associated with the main loadinginduc tan'ces';

Cent'to each other but separatedjby an air gap.

Amagnetic material armature is mounted in the airy gap and s, movable,t'owardand away from.

illustrating one form which: the invention may take and in which: y b Ib r Fig. 1 is a top; view of amountingof a pair of auxiliary inductancesfor use with-phantom cir..

Each auxiliary inductance consistsof windings mountedon twoC-shapedcoresso ar ranged that the free ends of the cores areadjae phantomtelephonelcircu'it.

Referring now to Figs." 1 and 2' a base plate 5 of a non-magnetic andelectrically non-conduc- I ENraq-OFFI'CEY Fig. 3 illustratesschematically the application tive material and of the 'general 'formshown is .10 may. beof brass or other tensilenoni-magnetic material sothatthere'is sufficijent spring I i V V action" to hold roan in positionwhen iti's Another'object' of'this invention is the 'reduc snappedintothe portions. M

A member 12is provided as shown with a hole near the upper edge which isthreaded'to-receive notches providedin the forked H b r v v v rod 11substantially as shown.

A still further object isthe accurate balancing H of the electricalcharacteristics of the side and.

Piece 12 supports armature 13 of magnetic ma 'terial as fshown. Armature13 is fastened to piece 12 in any suitable manner. As indicated in thedrawing, a slot-'m ay'be cut along the" loweredge of piece l2 and'thearmature forced; into the slot.

The dimensions of armature 13 are'such that there is but slightclearance between its free edges and; the bottom and sides of the recessin plate 5. Coils 14 and 15 mounted on'cores 16 and 1'7 are forcedintothe recess and are hel'din posi tion by the friction between the sidesof the recess and the outside of the coil structures and betweenprojections? and 8 and the inside of the coil structures;- Ah, adhesivemay be used to increasethis friction, or a'clamp may be used. Leads 18,19, 20 and 21 provide the means for connecting the coils to externalcircuits. v

The coils and'armature are positioned so that the armature is in a planeparallel to thejplanes of the free'ends of cores 16"andl'7. With thestructure as just described, if rod 11 is turned about its axis by meansof a screwdrive'r or similar tool, armature 13 is caused to 'movein aplane parallel to the plane of the freeends'of the cores and approachesthe} free ends of one of the cores while receding from'the others. a Thereluctancesof the magnetic paths through the cores are changed due-tothe yarying air lio gaps and hence the inductances of the coils arechanged.

The use of the device of this invention is a loaded phantom circuit isshown schematically in Fig. 3. This is the well known phantom circuitarrangement consisting of one phantom circuit and two side circuits. Thetwo side circuits 22 and 23 form the sides of the phantom circuit. Therepeating coils for such a circuit are shown generally at 24 and 25, theloading coils for the side circuits are indicated at 26 and 2'7, themain phantom circuit loading coils are indicated at 28 and the auxiliaryadjusting coils at 29. It is to be understood that the auxiliary coils29 may be used in the side circuits as well as the phantom circuit.

No further description of the circuit is believed necessary. It is alsobelieved that it will be readily apparent that if the phantom loadingcoils are slightly unbalanced, such unbalance is easily taken care of bychanging the location of armature 13 relative to the free ends of thecores of the auxiliary inductances. This is done by turning the screw11.

The device as described will adjust for inductance or neutralizecapacitance unbalance, in the circuit. To adjust for resistanceunbalance one of the leads of the pairs 18-19, 20-21, is left somewhatlonger than necessary and by means of a clip connector the correctlength of the lead is determined. The surplus length 01' the lead is cutoff and connection made to the external circuits.

After the adjustments have been made, a cover of a non-magnetic andpreferably non-metallic material isplaced over the device and any extralength of lead required to efiect the resistance balance may be foldedand secured beneath the cover.

With devices such as described variations as high as microhenries havebeen obtained. This is sufiiciently large to adjust for any variationsmet in practice. As to resistance adjustment, practically any variationcan be obtained but usually not more than .08 ohms adjustment isrequired which can be obtained as outlined above.

The advantages of the present device can be better appreciated when itis realized that for-- 1 merly adjustments were made by adding lumpedstruction avoids capacitance unbalance and the simple resistanceadjustment is necessarily very small and can readily be made in themanner that has been pointed out. One such device having permalloy dustcores which has been found very satisfactory has the following overalldimansions-length 3 width about 1 /2 and a height of about It is to beunderstood that, whereas the present invention has been described inconnection with the loading coil of a phantom circuit, it is not to belimited to such use, but may be applied wherever adelicate inductanceadjustment is required without changing. the other electricalcharacteristics of the circuit.

The specific structure of the invention as described may be modifiedwithout departing from the spirit and scope of the invention as definedin the appended claims.

What is claimed is:

1. A variable inductance device comprising a plurality of main windings,a plurality of auxiliary windings, each one of said auxiliary windingsconnected in series with and adapted to cooperate with a specific one ofsaid main windings,

and common means adapted to vary the inductance of certain of saidauxiliary windings in one direction while simultaneously varying theinductance of certain others of said auxiliary windings in the oppositedirection.

2. A variable inductance device comprising a plurality of main windingsarranged in pairs, a plurality of auxiliary windings also arranged inpairs, each pair of said auxiliary windings adapt- .ed to cooperate witha specific pair of said main windings, and means adapted to varyconversely the inductance of said auxiliary windings in pairs.

3. A variable inductance device comprising a plurality of main windingsarranged in pairs, a plurality of auxiliary windings also arranged inpairs, each pair of said auxiliary windings adapted to cooperate with aspecific pair of said main windings, and means adapted to increase theinductance of one winding of an auxiliary pair while simultaneouslydecreasing the inductance of the other winding of said pair.

'4. A variable inductance device comprising a plurality of main windingsarranged in pairs, a plurality of auxiliary windings also arranged inpairs, each pair of said auxiliary windings adapted to cooperate with aspecific pair of said main windings, and means adapted to varyconversely the reluctance of the magnetic circuits of said auxiliarywindings in pairs.

5. A variable inductance device comprising a plurality of main windingsarranged in pairs, a plurality of auxiliary windings, also arranged inpairs, each pair of said auxiliary windings adapted to cooperate with aspecific pair of said main windings, magnetic material cores associatedwith said auxiliary windings, a magnetic material armature for each pairof said auxiliary windings, and means adapted to vary the position ofsaid armature relative to the endspi said cores.

6. A variable inductance device comprising a plurality of main windingsarranged in pairs, a plurality of auxiliary windings also arranged inpairs, each pair of said auxiliary windings adapted to cooperate with aspecific pair of said main windings, magnetic material cores for saidauxiliary windings, the cores of each pair of said windings beingarrangedso that their free ends are adjacent each other, an armaturepositioned between the free ends of each pair of cores, and meansadapted to move said armature toward the free ends of one core and awayfrom the free ends of the other core.

7. An inductance adjusting coil for use in connection with maininductance coils, said adjusting coil comprising auxiliary inductancewindings mounted on C-shaped cores, each of said auxiliary windingsadapted for connection in series with a specific winding of one of themain inductance coils, said auxiliary windings arranged in pairs, anarmature for each pair of auxiliary windings, and means to move saidarmature toward one C-shaped core of a pair while simultaneously movingit away from the other core of the pair whereby the inductances of thewindings of the pair are conversely varied.

8. In combination witha main inductance coil having a pair of windings,a variable inductance other, a piece of magnetic material mountedbetween the tree ends of each pair of cores, and means adapted to movesaid piece of magnetic material toward the Iree'ends of one core or a.pair and away from the free ends of the other coreot the pair.

. RALPH M. C.

